Disk drives are a type of information storage device that store information on at least one spinning disk. Other types of information storage devices include, for example, magnetic tape drives which retrieve stored information on magnetic tape (e.g. linear tape drive, helical scan tape drive). There are several types of disk drives. For example, there are so-called floppy disk drives, which store information on removable magnetic disks. There are also optical disk drives, which typically retrieve information stored on removable optical disk media. Magnetic hard disk drives typically store information on non-removable rigid magnetic disks. Also for example, there are magneto-optical disk drives, which share some of the characteristics of optical disk drives and magnetic hard disk drives.
The contemporary magnetic hard disk drive 10 that is shown in FIG. 1 includes a head disk assembly (HDA) 12 and a printed circuit board assembly (PCBA) 14. The HDA 10 includes a baseplate 16 and cover 20 that together house annular magnetic disks 22, 24. Each of the disks 22, 24 contains a plurality of magnetic tracks for storing data, disposed upon its opposing disk major surfaces. The head disk assembly 12 further includes a spindle motor 26 for rotating the disks 22, 24 about a disk axis of rotation 28. The spindle motor 26 includes a spindle motor hub that is rotatably attached to the baseplate 16 of the HDA 12. Disks 22, 24 may be stacked and separated with one or more annular disk spacers 21 that are disposed about the hub, all held fixed to the hub by a disk clamp 11.
The HDA 12 further includes a head stack assembly (HSA) 28 rotatably attached to the base plate 16 of HDA 12. The HSA 28 includes an actuator body 30 having a pivot bearing cartridge engaged within a bore for facilitating the HSA 28 to rotate relative to HDA 12 about an actuator pivot axis 46. One or more actuator arms 32 extend from the actuator body 30, and one or more head gimbal assemblies (HGA) 34 are attached to a distal end of each actuator arm 32. Each HGA includes a head (not visible in a drawing of this scale) for reading and writing data from and to a disk surface. The HSA 28 further includes a coil 50 that interacts with one or more magnets 54 that are attached to baseplate 16 via a yoke structure 56, 58, to form a voice coil motor for controllably rotating the HSA 28. HDA 12 includes a latch 52 rotatably mounted on base 16 to prevent undesired rotations of HSA 28.
The PCBA 14 includes a servo control system for generating servo control signals to control the current through the coil 50 and thereby position the HSA 28 relative to tracks disposed upon the surfaces of disks 22, 24. The HSA 28 is electrically connected to PCBA 14 via a flex cable assembly 60, which includes a flex cable and a flex cable support bracket that attaches to the base plate 16.
All types of disk drives typically include a baseplate, to which a spindle motor and head (or lens) actuator are affixed. It is known in the art that casting is a low-cost manufacturing method for fabricating the disk drive baseplate. Typically cast baseplates include regions that are subsequently machined to create registering surfaces to facilitate precise positioning of certain disk drive components relative to each other (e.g. ensuring that the disk drive spindle, actuator, and/or ramp components are positioned relative to each other at the correct Z-height).
It is also known in the art that it may be advantageous to include an arcuate shroud wall closely around the outer diameter of the disk(s), as a feature of such a baseplate, to reduce or attenuate dynamic excitation of certain disk drive components (e.g. disks, HSA). However, the closer to the disk that a designer specifies the arcuate shroud wall to be, the less manufacturing variation may be allowed in the fabrication of the baseplate.
Unfortunately, reducing variation in the baseplate manufacturing process may require the election of a higher-cost initial fabrication process than casting, and/or the need for excessive machining steps after the initial casting of the baseplate shape. Moreover, given the intense price competition and low profit margins that characterize the information storage device industry, it may be commercially impractical to select a higher cost manufacturing process for baseplate fabrication. Consequently, the benefit of tight clearance between the arcuate shroud wall and the disk(s), in inexpensive disk drives, may not be practically obtainable in a high-volume manufacturing environment with acceptable manufacturing cost and yield.
Therefore, there is a need in the art for a baseplate design and/or casting method that will practically enable tighter tolerances between a cast baseplate and a disk, with associated cost and yield that is acceptable for the high-volume manufacture of inexpensive disk drives.